1. Field of the Invention
The invention relates to an attachment for a stringed instrument, such as a guitar, and more particularly to an improved pressure bar for a capo tasto which is secured to the stem of the stringed instrument so as to clamp all of its strings to its fret board at a temporary fret position.
2. Description of the Prior Art
U.S. Pat. No. 390,612, entitled Capodastro for Guitars, issued to George D. Moffat on Oct. 2, 1888 describes a capo tasto which includes a C-shaped mounting member, having a first end and a second end, which is adapted to being disposed about the stem of a stringed instrument perpendicular to the longitudinal axis of the stem. The capo tasto also includes a pressure bar, having a first end and a second end, which is hinged or pivoted at a point intermediate to its first and second ends to the first end of the C-shaped mounting member and disposed in the same plane as the C-shaped mounting member. The pressure bar may be provided with a pad of cork or any other suitable material so that the pressure bar does not injure the strings. Furthermore, the pressure bar is self-adjusting and is free to tilt about its point of pivotal suspension so that it can properly depress the strings regardless of the capo tasto's position on the guitar-stem. The capo tasto finally includes a cam level mechanically coupled to the second end of the C-shaped mounting member and disposed in the same plane as the C-shaped mounting member so that the cam lever is parallel to the transverse axis of the guitar-stem. The cam lever is a disc which is eccentrically pivoted upon the second end of the C-shaped mounting member. An alternative embodiment of this capo tasto may include a bearing plate, that is operated by an adjusting screw so that the capo tasto may be clamped to the guitar neck. The inability of this capo tasto to center itself makes it difficult for a musician to easily and speedily change from one fret position to another fret position.
Two of the most commonly used capo tastos are the Bill Russell capo and the Jim Dunlop capo. The Bill Russell capo is the subject of U.S. Pat. No. 1,788,636, entitled Capo Tasto, issued to Willard H. Russell on Jan. 13, 1931 and includes a rubber pressure bar, which presses against the strings of a stringed instrument, a rigid reinforcing plate which is positioned inside of or on top of the rubber pressure bar and to which the rubber pressure bar is secured, an elastic strip, a portion of which is secured to a first lug on the rubber pressure bar at one end extending over the top of the rubber pressure bar, and secured to a second lug on the rubber pressure bar. The capo tasto is secured to the stem of the stringed instrument by wrapping the remaining portion of the elastic strip about the bottom surface of the stem. The tension on the elastic strip is maintained by a plurality of eyelets positioned on the elastic strip to which a set of pins are coupled. The Jim Dunlop capo is the subject of U.S. Pat. No. 3,185,012, entitled Capo Tasto, issued on Nov. 3, 1965 to James Dunlop and includes a channel of a roughly U-shaped cross-sectional contour molded from plastic, the side flanges which are arranged to diverge slightly and have bevelled end edges, a non-elastic cord is coupled to a cam lever, which is aligned perpendicular to the longitudinal axis of the stem of a stringed instrument on which it is placed and which secures the capo tasto in place on the stem of the stringed instrument.
The disadvantages of both the Jim Dunlop capo and the Bill Russell capo is that a musician cannot easily and speedily change from one fret position to another fret position and he must use both hands to do so. Furthermore, neither of these capos is very durable and each of them has a tendency to wear out quickly.
The inventors are also aware of another set of capos which are manufactured by Hamilton and each of which includes a U-shaped mounting member, having a base, a first arm and a second arm, also a mounting bar, having a first end and a second end, with its first end pivotally hinged to the first arm of the U-shaped member and its second end adapted to latch to the second arm of the U-shaped mounting member, a pressure bar, which mounts on the mounting bar. One of these capos has a screw adjusted pressure plate, that is disposed on the base of the U-shaped mounting member. The other capo is secured to the stem of a stringed instrument by a positively engaging spring device disposed on the base or the U-shaped mounting member. These capos are aesthetically unattractive and require the musician to use his two hands to change from one fret position to another fret position.
U.S. Pat. No. 3,722,346, entitled Capo, issued to Pete P. Valentino on Mar. 27, 1973, teaches an improved capotasto for use in tuning string instruments of the type having a fingerboard including a plurality of transversely oriented frets and a plurality of substantially parallel strings traversing the frets. The capo includes an elongated bar that is repositionable along the fingerboard of a string instrument for uniformly varying the pitch of all of the string. The pressure bar of the capo has a plurality of orthogonally related planar surfaces. The pressure bar of the capo may also be cylindrical.
U.S. Pat. No. 3,823,247, entitled Capo Tasto issued to Herbert Bauerfeind on July 9, 1974, describes a capo tasto which includes a pressure bar, a bowed clamp member hinged to one end of the pressure bar, and a device which interengages the other, unhinged end of the pressure bar in order to secure the capo tasto to the guitar. The pressure bar has a comb-like part, the teeth of which are closely spaced and adapted to press on the strings of the instrument. The disadvantage in using this capo tasto is that a musician must use both his hands to change from one fret position to another fret position. The advantage of this capo tasto is its aesthetic qualities in that it is practically invisible when placed on a stringed instrument.